People in general sometimes turn off their brain when going online.
How many blogs, social sites and the like have you seen where people post the most intimate, embarrasing and private stuff for everybody to see and read and not think twice of it.
HR people nowadays routinely use the net to check on applicants and see who they really are and sometimes they see pictures of the person stone cold drunk amidst a gangbang and such.. try getting a good job after exposing yourself like that.
Personally i don't get social sites like Facebook, myspace etc.. i have all the contact info for my friends and if they want i'll tell them how my days ways.. no need telling strange people that i couldn't take a dump in two days.